1. Field of the Invention
The present invention relates generally to a communication connection merge method and a node to be employed therein. Particularly, the invention relates to a communication connection merge method and node to be employed therein, which merges a plurality of communication connection set in a connection-oriented network during communication with simultaneously updating collateral parameter on a common path performing merging.
2. Description of the Related Art
Conventionally, a communication connection merge method and a node to be employed in the same is used for merging communication connections which make transfer path from a merge point to an egress label switching router (LSR) common, upon setting a label switching path (LSP) in a MultiProtocol Label Switching (MPLS) network as disclosed in Internet Draft, draft-ietf-mpls-arch-06.txt, August, 1999 and Internet Draft, draft-ietf-mpls-ldp-06.txt, October, 1999, for example.
Here, merge means consolidating a plurality of transfer paths into a single transfer path at a mid-way. In a path from a merge point to an egress LSR, the same transfer path identifier (here, a label of MPLS) is used for the packet. By performing merging, number of transfer label of LSR can be reduced to contribute for operation of a large-scale network.
Next, the prior art will be discussed with assumption that connection-oriented network being MPLS network, communication connection being LSP and node being LSR. Referring to FIG. 9, the MPLS network 1 is constructed with LSRs 101 to 104. Respective LSR 101 to 104 are connected through links 201 to 203. Data is exchanged through these links 201 to 203. On the other hand, an LSP 301 routed from the LSR 101 to the LSR 103 via the LSR 102 is present.
Here, consideration is given for the case that new LSP is established from the LSR 104 to the LSR 103, at first, the LSR 104 feeds an LSP setup request 401 for the LSR 103 to the LSR 102 using an LSP setting protocol. The LSR 102 receiving the LSP setup request 401 makes judgment whether or not LSP to be merged to the LSR 103 is present. If present, merging is performed. Here, since the LSP 301 which makes the path to an egress router in common, is already present, merging can be performed.
Upon performing merging, setting of LSP is not requested beyond the LSR 102 (namely to the LSR 103), an LSP setup response 402 is returned to the LSR 104. Then, with taking the LSR 104 as starting point, an LSP 302 to be merged to the LSP 301 is set in the LSR 102.
In the conventional communication connection merge method, collateral parameter (called parameter), such as request bandwidth or the like owned by the LSP cannot be merged upon performing merging. This is because the merging is performed without modifying the parameter of existing LSP.
As an example of such parameter, there are parameter relating to traffic, such as request bandwidth, delay or the like, parameter relating to policy, such as Virtual Private Network (VPN) identifier, preference or the like.
On the other hand, in the conventional communication connection merge method, once merging is performed, the merged LSP cannot be branched at the mid-way. Therefore, even if the parameter, such as request bandwidth or the like owned by the LSP could be merged together, the range of application is limited to the case where transfer path to the egress LSR can be common. For example, even if the most portion of the transfer path is common, merging cannot be performed if the egress LSR is different.